Last week Russia and the US signed the new strategic arms reduction treaty (Start) signalling a significant shift in the focus of America's nuclear strategy, from its former cold war foes to so-called rogue states. This week at the nuclear summit in Washington China agreed for the first time to work with the United States on a possible sanctions regime against Iran. While the momentum for new UN sanctions against Iran is building so to are fears that military intervention against Tehran is becoming more likely. President Obama's instincts will ensure he does everything in his power to avoid military conflict with Iran – but he is up against hawkish elements at home.

Last month US senator Lindsey Graham told an audience that if used, military force against Iran should be employed "in a decisive fashion" ensuring that Iran no longer has "one plane that can fly or one ship that can float". This type of combative rhetoric is nothing new from Washington's hawks but Senator Graham's words reflect a growing militancy within a Congress which last year authorised an additional $46bn in emergency military funds. At the end of March, a resolution was circulated in the House of Representatives explicitly endorsing an Israeli military strike on Iran if "no other peaceful solution can be found within reasonable time". The type of "peaceful solution" and the time frame they would consider "reasonable" was not specified.

It was recently reported that hundreds of "bunker-buster" bombs are being shipped from America to the US military base on the island of Diego Garcia and that the US government has signed a contract with a shipping firm to transport 19 ammunition containers to the island. The containers will include 195 smart guided Blu-110 bombs with penetrators and 192 massive 2000-pound Blu-117 bombs. The US already has massive military force in the Gulf and has been carrying out large-scale naval manoeuvers in the Atlantic with the British and French.

On coming into office Obama made a clear break with George Bush's Iran strategy by demonstrating a willingness to engage in direct negotiations with Tehran without preconditions. In his broadcast to Iran and his Cairo speech, he publicly recognised the Ayatollahs as the legitimate representatives of the Iranian people, acknowledged Iran's right to enrich uranium and talked openly about the CIA's role in the overthrow of Mossadegh in 1953. Last October, he held direct talks with the Iranians in Geneva after which the Financial Times noted that President Obama "has got more out of Iran in eight hours than his predecessor's muscular posturing did in eight years".

Obama also inherited a US military machine whose plans for an attack on Iran were already well advanced and he faces a conservative media and a public so unfamiliar with a foreign policy based on patient diplomacy and consensus-building that many equate it to weakness.The latest round of sanctions will involve stringent inspection requirements of all goods entering or leaving Iran and an embargo of refined petroleum products to Iran. The naval blockade required to enforce the sanctions – no doubt involving the Royal Navy – could well take us to the brink of war. As we have seen in the Gulf of Hormuz over recent years, skirmishes with the Iranian navy in the region have a tendency to escalate.

At the Geneva talks the proposed agreement devised by the US would have seen Iran exchange most of its current stockpile of low-enriched uranium for fuel rods from Russia and France. This "fuel-for-fuel" swap was largely accepted by President Mahmoud Ahmadinejad but, concerned by previous "broken promises", he proposed that the International Atomic Energy Agency (IAEA) assume control of the low-enriched uranium in Iran until the fuel rods are delivered. As a step towards a resolution of this protracted problem, Iran's counter-proposal seemed positive, but it was dismissed. Instead the US seem unwilling to negotiate further, regarding the proposed agreement as a "take it or leave it" offer.

For the US to view Iran's complete cessation of all enrichment activities as the goal of nuclear negotiations with Tehran is not only unrealistic but to a certain extent unnecessary. President Amadinejad is unlikely to give up enrichment activities which he regards as his nation's inalienable right. While many people have genuine concerns that Iran is intent on developing nuclear weapons, the way to ensure that Iran does not become a nuclear-armed nation is not to isolate Tehran. Instead rigorous international monitoring activities need to be reinstated. Arguments about the possible timeline for Iran to acquire a nuclear weapons capacity become academic if we ensure the Iranian co-operation with the IAEA's inspections regime.

Having gained new respect on the Arab street for his condemnation last month of the Israeli settlement policy and greater legitimacy in his call for nuclear non-proliferation by himself embarking on arms reductions, President Obama should take this opportunity to continue negotiations with Iran rather than pushing for further sanctions. Neoconservatives may try to convince Obama that as the sole global superpower, America must seize this moment to secure her position in the region and ensure control of diminishing oil and gas reserves. They may argue that it is preferable to launch a pre-preemptive attack against Iran sooner, while the US military machine is in the region, rather than later when Iran has become even stronger. But such an attack, based on the principle of anticipatory self defense and launched before all peaceful routes have been exhausted, would surely not sit easily on Obama's conscience. We can but hope that President Obama remains a man led by his beliefs.